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Environmental Checklist Hazards and Hazardous Materials <br /> Initial Study – Mitigated Negative Declaration 53 <br />d. Would the project be located on a site included on a list of hazardous material sites compiled <br />pursuant to Government Code Section 65962.5 and, as a result, would it create a significant <br />hazard to the public or the environment? <br />According to the Phase I and II ESA, the project site was previously contaminated by total petroleum <br />hydrocarbons, volatile organic compounds (VOCs) and semi-volatile organic compounds (WSP <br />2017). Therefore, construction operations on the project site that disturb soil could result in <br />exposure of construction workers or the environment to hazards. In addition, should contaminated <br />soil remain onsite after construction, soil vapor intrusion in the building could occur, exposing future <br />workers to health hazards. <br />However, as discussed in the Existing Setting above, the soil contamination onsite was sufficiently <br />removed in 1996. All 2016 soil gas sample results were below the commercial/industrial ESLs for soil <br />gas vapors below building slab or sub-slab. Based on the soil gas results, WSP concluded that the <br />potential vapor intrusion is very low soil vapor mitigation measures were not needed to reduce <br />potential impacts. This indicates that the presence of contamination is not at levels that would <br />expose potential future onsite employees to significant hazards. <br />Six monitoring wells are currently present on the project site. The data taken from the groundwater <br />monitoring wells are used by DTSC to ensure ongoing protection of human health from the DWA <br />plume over time. By monitoring the wells, they can make sure that the groundwater contamination <br />does not migrate, or if it does, they can take action to protect nearby occupants and sensitive <br />receptors from hazardous exposures. As discussed in the Existing Setting above, the DTSC agreed to <br />the decommissioning of four of the six monitoring wells onsite (DTSC 2017). The two monitoring <br />wells to be left onsite are located along Alvarado Street in what would be the parking lot of the <br />project. As such, DTSC would be able to maintain access to these wells after development of the <br />project. The two monitoring wells will be used by DTSC to collect groundwater elevation data and <br />groundwater samples for continued monitoring of the regional DWA plume. The following <br />mitigation measure would be required to maintain the integrity of the monitoring wells during <br />construction and site use and permit DTSC access to the wells for ongoing monitoring of the <br />regional DWA groundwater plume. <br />Mitigation Measures <br />The following mitigation measure shall be implemented prior to and during ground-disturbing <br />activities associated with construction onsite: <br />HAZ-1 Monitoring Wells Protection and Access. The project applicant shall ensure the two <br />monitoring wells that will remain on the project site must remain intact and <br />undamaged during construction activities of the project. The two monitoring wells <br />must also remain accessible to the DTSC for future testing. <br />Implementation of Mitigation Measure HAZ-1 would ensure the wells that monitor the existing <br />regional plume would remain and DTSC access would continue. This would allow DTSC to monitor <br />the regional DWA plume and provide corrective action as necessary. These measures would reduce <br />impacts to a less than significant level. <br />LESS THAN SIGNIFICANT WITH MITIGATION INCORPORATED <br />350